1. Field Of The Invention
The invention relates to emplacement of tubulars in extended reach boreholes and other depth extended apertures such as highly deviated casing strings and horizontal pipelines. In one aspect presently considered to be of premier importance, the invention relates to emplacing an anisotropically tailored tubular into an extended reach borehole.
2. Brief Description of the Prior Art
With continued depletion of hydrocarbon reserves and continued very trying economic conditions in the oil industry, improved methods for production of hydrocarbons, particularly from marginal reservoirs, is of high importance. One technology that has recently come into ever increasing use is the employment of highly deviated or extended reach horizontal boreholes to produce hydrocarbon-containing reservoirs. This is often advantageous in that remote reservoirs can be produced from a central location. Some examples are as follows: an underwater reservoir may in some circumstances be produced from an on land site with considerable economic and environmental advantages. A single platform can be employed to tap radially extended subterranean reservoirs. Certain types of reservoirs such as those found in undulating ancient sand dunes can advantageously be produced by an extended reach borehole.
When highly deviated or extended reach boreholes reach great lengths, for example, measured in several thousands of feet or in miles or kilometers, it becomes very difficult to emplace tubulars such as tubing strings, or tubulars which are employed to run logging tools and the like over considerable deviated or horizontal distances in order to reach the extent of the producing reservoirs tapped by the boreholes. Presently, extended reach boreholes have been drilled over 1000 meters in a lateral direction. The method of this application may make much greater distances feasible.
Emplacing the tubular must overcome the frictional forces of the horizontal or highly deviated borehole, and over extended distances, this becomes very difficult because of frictional forces of the walls of the borehole on the outer surface of the tubulars. The problem eventually becomes analogous to trying to push a rope up hill, and for any particular system, a limit of how far the tubular can be pushed into the depth extended aperture is reached. The same type of problem occurs with emplacing tubulars in horizontal pipelines and the like. For example, it is often desired to emplace a tubular into a horizontal pipeline in order to dissolve paraffin or other materials which are restricting flow in the pipeline.
Recently, there has also been much interest in the use of composite tubulars in oil industry applications, for example, as tubing strings or as employed to emplace logging tools and the like, particularly in highly deviated or extended reach boreholes. This is particularly attractive because such tubulars can often be fabricated in great lengths. Such coiled tubing strings, as they are commonly known, are simply unreeled as they are extended into extended reach boreholes and the like by means of capstan wheel arrangements, grip-and-push mechanisms, or tracked tubing injectors. The prior art contains numerous disclosures of this technology.
One basic reference on such composite materials is the "Primer On Composite Materials: Analysis" Volume III, Progress and Materials Science Series, Technomatic Publishing Company, Inc., 750 Sumner Street, Stanford, CN 06901 (1969). This reference discusses the general theory of anisotropically tailored materials including tubulars fabricated of helically wound composites which will provide rotation upon application of tension or compression along the long axis of the tubular. Conversely, application of torsion to the tubular shows an increase or decrease in the length of the tubular. The reference otherwise provides a generalized disclosure of fabrication of and characterization of anisotropically tailored composites.
The invention of this application utilizes these characteristics to provide a method for emplacing tubulars in depth extended apertures, thus providing a solution for the problem faced by the art, as set out above.